1. Field of the Invention
The present invention relates to a nematic liquid crystal composition. More particularly, the present invention relates to a nematic liquid crystal composition having a high phase transition temperature and a high response speed.
2. Description of the Related Art
Recently, an information processing technology and a technology of manufacturing information processing devices have been developed. With developments of the technologies, a massive data may be processed in short time. Thus, a display device that displays the processed data has been introduced in various fields.
With a rapid development of a semiconductor technology, electronic devices are demanded to be small in size, light in weight and low power consumptive. In recent years, a flat panel display apparatus with the above characteristics is in strong demand.
In particular, demands for a liquid crystal apparatus device have increased since the liquid crystal display device requires low power consumption and low operation voltage while exhibiting an excellent display quality as bright as a display apparatus using a cathode ray tube. The liquid crystal display apparatus is widely used in various electronic devices.
The liquid crystal display apparatus may be applied to display devices such as a notebook computer, a computer monitor or a television set. As for the television set, a twisted nematic (TN) liquid crystal display apparatus, an in-plane switching (IPS) liquid crystal display apparatus or a vertical alignment (VA) mode liquid crystal display apparatus may be used. The IPS liquid crystal display apparatus and the VA mode liquid crystal display apparatus have a wide viewing angle, but a slow response speed. Thus, the IPS liquid crystal display apparatus and the VA mode liquid crystal display apparatus may not be suitable for displaying a moving image. In addition, manufacturing yields of the apparatuses are low and manufacturing costs of the apparatuses are high.
Alternatively, the TN liquid crystal display apparatus has a high manufacturing yield and a low manufacturing cost. The TN liquid crystal display apparatus, however, has a narrow viewing angle and a low response speed.
Liquid crystal requires a low viscosity for a high response speed, a high dielectric anisotropy for low operation voltage, and a nematic phase over a wide range of temperature. Birefringence of the liquid crystal is preferably at least about 0.20 at about 25° C.
Generally, each of the TN liquid crystal display apparatus, the IPS liquid crystal display apparatus and the VA mode liquid crystal display apparatus has a response speed of about 20 ms to about 30 ms. An increase of the response speed in the above apparatuses, however, is required for displaying a moving image.
A viewing angle of a liquid crystal display apparatus has been improved by use of a compensation film. The response speed, however, primarily depends on characteristics of the liquid crystal. Thus, a novel liquid crystal composition that exhibits a high response speed is required.
To display an image in the liquid crystal display apparatus as brightly as a display apparatus using the cathode ray tube, a backlight assembly is used as a light supply source. The backlight assembly, however, may generate a heat in the lamp tube of the backlight assembly.
Generally, a liquid crystal display apparatus has two substrates and a liquid crystal layer interposed between the two substrates. Electric power from an external power supply is applied to electrodes on the substrates. The liquid crystal transmits or blocks an external light generated from the backlight assembly to display data as an image. The backlight assembly is disposed near the liquid crystal. Thus, the heat generated from the backlight assembly may be transferred to the liquid crystal.
Accordingly, a liquid crystal composition with a high phase transition temperature is required. Currently used nematic liquid crystal compositions for a TN liquid crystal display apparatus, an IPS liquid crystal display apparatus or a VA mode liquid crystal display apparatus may have a phase transition temperature of about 70° C. to about 80° C., which is not preferable for a display apparatus requiring a high brightness.